Sawafi (the crown lands of the Sawad)

Sawafi in al-Baladhuri are the lands of al-Sawad that Umar ibn al-Khattab (may God be pleased with him) set aside for the Muslims, without leaving them in the hands of their people and without imposing on them the usual land tax. ¹

Ibn Abi Hurra, from his father, counted ten kinds: the land of those killed in war; the land of those who fled; every land of Khusraw; every land of his household; every place where water collects; every monastery that is increased; every plot Khusraw chose for himself; and the land of the exiles. ¹

Its sawafi reached seven million dirhams, and remained so until the skulls fell in the days of al-Hajjaj, when the register was burned and each people took what was next to them. From them 'Uthman ibn Affan (may God be pleased with him) cut out the first allotments of Iraq, as Musa ibn Talha says. ¹

A further source is needed: the figures and details here come from al-Baladhuri's account alone.